national security agency is directing billions of records of mobile phone locations every day. how a mobile phone can be turned into a tracking device. >> wherever you are in the world, as soon as you switch on your mobile phone, it tries to connect to the mobile network. usually through the closest tower. as soon as it does, your phone number is logged with the network, along with which tower you have connected to. which means your location. >> if you are on the move, anyone with tract your rout. by gathering and processing 5 billion records each day, to see which individuals are traveling or meeting together. here is how it works. >> you may be connected to a tower, along with 100 other people. you move down the street, and automatically connects to the next closest tower. say 20 of the 100 are moving in the same direction you move further down the road, and say just five of the original 100 people, join you. a couple more towers and some time later just one person who is mirrored your movements. the assumption, you have some reason for being together. >> it raise as lot of q